1. Field of the Invention
The present invention relates to a semi-transmission liquid crystal display (LCD) device and a fabricating method thereof, and more particularly, to a semi-transmission LCD device capable of enhancing a reflection efficiency of light by introducing external light to a reflection portion on an array substrate of a thin film transistor by concavely forming an overcoating layer on a color filter substrate, and capable of enhancing a transmission efficiency of light incident from a backlight, and a fabricating method thereof.
2. Description of the Background Art
As information society develops in the 21th century, a flat panel display device having a thin and light characteristic and requiring a low power consumption is being spotlighted.
The flat panel display device is divided into a light emitting display device and a light receiving display device according to its spontaneous light emitting characteristic.
The light emitting display device includes a plasma display panel device, a field emission display device, an electro-luminescence display device, etc., and the light receiving display device includes a liquid crystal display (LCD) device.
The LCD device has excellent characteristics in a resolution, a color display, a picture quality, etc., thus to be actively applied to a notebook or a PC monitor.
The LCD device is an apparatus for displaying an image by attaching two substrates to each other, each substrate having an electrode for forming an electric field, by injecting a liquid crystal material between the two substrates, by moving liquid crystal molecules by an electric field generated by applying a voltage to the two electrodes, and thereby controlling a light transmittance.
However, since the LCD device is a light receiving display device that does not spontaneously emit light, an additional optical source is required.
Accordingly, the LCD device displays an image by controlling an amount of light according to arrangement of a liquid crystal, the light incident onto an LC panel from a backlight disposed at a rear surface of the LC panel.
An electrode for forming an electric field that determines arrangement of an LC is formed of a transparent conductive material, and two substrates each having the electrode are formed of transparent substrates.
The LCD device is a transmission LCD device.
Since an additional optical source such as a backlight is used, a light image can be implemented even in a dark place. However, the backlight causes power consumption to be increased.
In order to solve the problem, a reflection LCD device has been proposed.
The reflection LCD device controls a light transmittance according to arrangement of an LC by reflecting natural light or artificial light, thereby decreasing power consumption.
However, the reflection LCD device using external natural light or artificial light as an optical source can not be used in a dark place.
Accordingly, a reflection/ transmission LCD device for a reflection mode and a transmission mode has bee proposed.
A general semi-transmission LCD device will be explained in more detail.
FIG. 1 is a sectional view showing the conventional semi-transmission LCD device.
As shown, the conventional semi-transmission LCD device comprises a first substrate 10 and a second substrate 30 having a predetermined gap therebetween, and an LC layer 40 interposed between the two substrates.
A gate electrode 12 is formed on the lower first substrate 10, and a gate insulating layer 13 is formed thereon.
Before the gate insulating layer 13 is formed, a gate line (not shown) connected to the gate electrode 12 is additionally formed.
Then, an active layer 14 and ohmic contact layers 15a and 15b are sequentially formed on the gate insulating layer 13. Then, source and drain electrodes 16a and 16b are formed on the ohmic contact layers 15a and 15b. 
The source and drain electrodes 16a and 16b constitute a thin film transistor (TFT) together with the gate electrode 12.
A data line (not shown) formed of the same material as the source and drain electrodes 16a and 16b is further formed on the gate insulating layer 13.
The data line is connected to the source electrode 16a, and is crossing a gate line (not shown) thus to define a pixel region.
A first passivation layer 17 formed of an organic material is formed on the source and drain electrodes 16a and 16b, thereby covering the TFT.
A reflector 18 formed of an opaque conductive material is formed at a pixel region on the first passivation layer 17. A second passivation layer 19 is formed on the reflector 18.
The second passivation layer 19 has a contact hole 19a through which the drain electrode 16b is exposed out.
A pixel electrode 20 formed of a transparent conductive material is formed at a pixel region on the second passivation layer 19.
The pixel electrode 20 is connected to the drain electrode 16b through the contact hole 19a, and serves as a transparent electrode. By the above process, a first alignment layer 21 is formed.
A black matrix 32 is formed on the second substrate 30, and color filters 33a and 33b formed of R, G and B are sequentially and repeatedly formed on the black matrix 32.
One of the color filters 33a and 33b corresponds to one pixel electrode 20, and the black matrix 32 covers the TFT and an edge of the pixel electrode 20.
An overcoat layer 34 for protecting and planarizing the color filters 33a and 33b is formed on the color filters 33a and 33b. The overcoat layer 34 is formed of an acrylic resin or a polyimide-based resin.
A common electrode 35 formed of a transparent conductive material is formed on the overcoat layer 34, and a second alignment layer 36 is formed on the common electrode 35.
A liquid crystal layer 40 is disposed between the first alignment layer 21 and the second alignment layer 36.
The liquid crystal is a twisted nematic LC, and an LC molecule 41 of the LC layer 40 is constantly arranged on the substrate with a pre-tilt angle.
However, the conventional semi-transmission LCD device is mainly used in a transmission mode since an amount of light introduced in the transmission mode is greater than an amount of light reflected in a reflection mode.